A magnetoresistive sensor utilizing magnetoresistive effect in which an electric resistance changes in accordance with change in an external magnetic field has been known as an excellent magnetic field sensor and has been put into the practical use as a read head of magnetic head which is the principal component of a magnetic storage apparatus. Since the magnetic storage apparatus is continuously progressing in reduction in size and higher speed transfer, higher performance is also required for a magnetic head for reading and writing information. Measures for realization of higher output and higher transfer rate may be listed as the principal subjects of the read head among such requirement. In regard to higher output, development and improvement of a magnetoresistive film have been conducted. For recording density of about 3×108 bits per 1 cm2, an anisotropic magnetoresistive (AMR) film has been used. For higher recording density, a giant magnetoresistive film (GMR) for attaining higher output has been developed. At present, further improvement has been conducted to such GMR. However, since it is feared that such GMR cannot provide sufficient output for the recording density higher than 9.3×109 bits per 1 cm2, investigation and development have been conducted for the tunneling magnetoresistive film and CPP-GMR film, allowing a current to flow through the stacking surfaces of sensing films, as the next generation magnetoresistive film of the GMR film.
A magnetic head using the AMR film and GMR film is remarkably different in structure from a magnetic head using the tunneling magnetoresistive film and CPP-GMR film. The former has a CIP (Current Into the Plane) structure where the sensing current flows in the in-plane direction of the magnetoresistive film formed of the AMR film and GMR film. magnetoresistive film. Meanwhile, the latter has a CPP structure where the sensing current is applied almost in the perpendicular direction to the plane of the magnetoresistive film formed of the tunneling magnetoresistive film and CPP-GMR film. Therefore, the electrodes for supplying the sensing current are provided in the manner that these electrodes are stacked on the magnetoresistive film.
As one of the peculiar subjects of a CPP structure head, it may be listed that a process is required to remove re-deposition deposited by the etching to the side wall of junction of the magnetoresistive film for detecting an external magnetic field. In general, the etching is conducted with a dry etching method, particularly with an ion milling method. However, in this case, a first etching process is conducted for executing the etching to almost the predetermined shape by irradiating the ion beam almost in the perpendicular angle to a substrate and thereafter a second etching process is conducted for removing re-deposition deposited to an edge in the sensor height direction of the junction by irradiating the ion beam in the shallower angle. In this process, since the ion beam is incident in the angle near to the comparatively perpendicular angle to the side wall of junction in the second etching process, a certain consideration is necessary to damage caused by the etching process more than the CIP structure which does not require the second etching process. Moreover, a problem also rises in the CPP structure head, in which when the second etching process is conducted, an edge in the sensor height direction easily becomes more steep, thereby a step is generated in the bottom surface of the upper magnetic shield layer, and such step will induce deterioration in the dielectric breakdown voltage between the upper magnetic shield layer and lower magnetic shield layer and instability in read performance resulting from magnetic shield layers.
A measure for higher transfer rate will become a problem peculiar to the CPP structure because measures for CIP structure head and CPP structure head, which are different in arrangement of electrodes for supplying the sensing current, are also different. In the CPP structure head, since electrostatic capacity C is generated with an upper electrode layer (an upper magnetic shield layer is also used in some cases) provided in the manner of stacking on the magnetoresistive film and a lower electrode layer (a lower magnetic shield layer is also used in some cases), the process for controlling these electrode layers not to becomes closer as required and the process for controlling the structure in the sensor height direction of these electrode layers for reproduction with good yield are necessary.
In regard to the shape of CPP structure head in the sensor height direction, references JP 2002-299726 A and JP 2003-298143 A disclose formation of a junction edge in the shape which is gradually curved in the CPP-GMR sensor. Moreover, the JP 2003-204096 A and JP 2004-118978 A disclose, in the TMR sensor, top surface of the pinned layer is flat and also disclose formation of a stepped junction edge having two straight tapers on the edges of upper layers over the pinned layer and lower layers under the pinned layer.
The patent documents JP 2002-299726 A and JP 2003-298143 A disclose a shape of a junction edge which is gradually curved in the sensor height direction but do not disclose a concrete structure of a magnetoresistive film so that an edge of any layer may have a steep taper and it is not apparent that an edge of any layer should have a gradual taper. In the patent document 2000-204096 A, a junction edge of the TMR sensor in the sensor height direction is formed in the shape of step including top surface of the pinned layer. However, an insulator film between the upper magnetic shield layer and lower magnetic shield layer is also formed in the shape of step, not consideration on reduction of electrostatic capacity. The patent document JP 2004-118978 A is similar to JP 2003-204096 A. These are different in the point that the pinned layer is longer than a free layer in the length of sensor height direction but shape of the pinned layer edge is not apparent. Moreover, an electrode for generating electrostatic capacity is formed of the upper magnetic shield layer and the pinned layer and distance between layers is shorter than the upper magnetic shield layer and lower magnetic shield layer. Accordingly, it can be said that any consideration is not taken on reduction of electrostatic capacity. In addition, the four patent documents of the related arts do not refer to an etching damage generated at a junction edge by the etching process to form the sensor height direction.